Technology disclosed in JP 07-55025B, for example, is proposed as an example of a power supply device that supplies power from a plurality of power supplies to a load. The power supply device disclosed in JP 07-55025B is provided with a plurality of DC power supplies, and a DC power supply synthetic circuit is provided between each DC power supply and a shared device. Furthermore, in the DC power supply synthetic circuits, paths from the DC power supplies are respectively provided with power MOSFETs so that a reverse current in each path can be blocked.
However, in each DC power supply synthetic circuit disclosed in JP 07-55025B, if a short circuit failure occurs in the MOSFET that is on the path from either one of the DC power supplies, a reverse current that is caused by power from the other power supply cannot be blocked, which is a problem. For example, in a case where a short circuit failure occurs in a MOSFET that is provided on a path for a reserve DC power supply, even if a MOSFET on a working DC power supply is turned OFF, the parasitic diode of this MOSFET and the MOSFET in which the short circuit failure occurred hold an electrically connected state. Therefore, a current flowing into the reserve DC power supply from the working DC power supply cannot be blocked, and there is a concern that overcharge will occur.
The present disclosure has been made in view of the above-described situation, and aims to realize a power supply device that can, even if an abnormality occurs in either one of the power supply units, block a current from flowing into the path for the power supply unit from the other power supply unit.